In this Sept. 4, 2012, photo, Newark Mayor Cory Booker addresses the Democratic National Convention in Charlotte, N.C. President Barack Obama may face the voters in two months, but several Democrats are already laying the groundwork for a future White House run. Up-and-coming Democratic stars like Maryland Gov. Martin O'Malley, Virginia Sen. Mark Warner, Booker and others are making the rounds before state delegations and at private events surrounding the Democratic National Convention in Charlotte. (AP Photo/J. Scott Applewhite)

CHARLOTTE, N.C. (AP) — If Cory Booker decides to run for president one day, he already has a personal connection to the first caucus state of Iowa.

The mayor of Newark, N.J., told about 60 Iowa delegates during a Democratic convention gathering that he was not only "a son of New Jersey but a grandson of Iowa." His 94-year-old grandmother was born in Des Moines, Booker said, and his family had ties to a now abandoned south-central Iowa mining town called Buxton, where many black families moved "to make a hope and a dream become a reality."

"This is the state that brought my family from deep poverty to the middle class. ... This is the state that will determine our destiny," Booker said of Iowa, pleading with the delegates for an all-hands-on-deck effort to re-elect President Barack Obama.

For Booker and a slate of rising stars in the Democratic Party, the national convention in Charlotte amounts to a try-out before local activists, financial donors and well-connected political heavyweights from early voting states like Iowa and New Hampshire and perennial battlegrounds such as Florida. Some already have established political reputations and a large network of donors, while others are trying to raise their national profiles.

Indeed, while Obama faces Republican Mitt Romney on Election Day in two months, 2016 isn't far off for a number of party leaders. The convention gives them a chance to size up the next generation of Democratic candidates.

Secretary of State Hillary Rodham Clinton, the most prominent Democrat in the 2016 equation, is half a world away, traveling on an 11-day, six-nation tour of the Asia-Pacific region. The former New York senator's popularity has grown steadily since her primary loss to Obama in 2008, but she has repeatedly denied that she's interested in running for president in four years. Nevertheless, the Clinton brand is on display this week, with former President Bill Clinton nominating Obama on Wednesday night.

Obama's running mate, Vice President Joe Biden, has not ruled out another presidential run and speaks Thursday night, shortly before Obama's address. The vice president, who would be 73 by 2016, arrived in Charlotte on Tuesday and planned to attend a private event Thursday night with top Obama donors at the NASCAR Hall of Fame.

Another 2016 contender, New York Gov. Andrew Cuomo, was keeping a low profile. Cuomo, whose sky-high approval ratings and political pedigree have generated talk of a future presidential bid, was traveling to Charlotte for Obama's address on Thursday but limiting his public events to a morning speech to his home state's delegation breakfast.

Any credible presidential candidate needs to raise tens of millions of dollars and have a strong enough network to support a national campaign, so a presidential campaign can be years in the making.

"It's really a combination of can you raise money and do you have a compelling political public brand?" said Chris Lehane, a former aide to Vice President Al Gore.

Up-and-coming Democrats like Booker, Maryland Gov. Martin O'Malley, Virginia Sen. Mark Warner, Minnesota Sen. Amy Klobuchar, Montana Gov. Brian Schweitzer and Los Angeles Mayor Antonio Villaraigosa were making the rounds before state delegations and at private events, introducing themselves to activists and trying to make a good first impression.

Some hoped to make a splash with their convention speeches, mindful of how Obama used his 2004 keynote address to catapult to prominence in the party.

San Antonio Mayor Julian Castro delivered the keynote address Tuesday, whipping up the crowd by vouching for Obama and lacing into the president's Republican rival. Castro, 37, the first Hispanic chosen to deliver a keynote address, ripped into the Republican ticket's economic policies.

"First they called it trickle down, the supply side," Castro said. "Now it's Romney/Ryan. Or is it Ryan/Romney?"

O'Malley was equally biting, questioning Romney's motives as the convention reached a primetime audience. "Mitt Romney and Paul Ryan now say they want to take America back ... and so we ask, back to what?"

O'Malley was holding a number of events in Charlotte during the week, including performances at an Irish pub by his Celtic rock band, O'Malley's March. O'Malley, the head of the Democratic Governors Association, had a prominent speaking slot Tuesday night and was appearing before Iowa's delegation on Wednesday morning. He snared a prime speaking role in Iowa next month, headlining Sen. Tom Harkin's annual fundraising steak fry.

But the Maryland governor's convention week got off to a rocky start on NBC's "Meet the Press" on Sunday, when he was asked if Americans were better off than they were four years ago. "No," O'Malley said, exposing a rift with Obama's campaign. O'Malley argued that the more pressing issue was that the nation is "not as well off as we were before George Bush brought us the Bush job losses, the Bush recession, the Bush deficits, the series of desert wars."

Warner, who made millions in the cellular phone industry, joked to the Florida delegation that he was the only politician who would ask them to "please leave your cellphones on" during his speech. A former Virginia governor, Warner offered a firm defense of Obama's policies and efforts to revive the economy.

"America is better off today than it was four years ago with this president," Warner said.

After Villaraigosa wrapped up his speech to the Iowa delegation, organizers presented the mayor with a gift bag that included a map of Iowa and announced he would headline the state party's annual fundraiser, the Jefferson-Jackson dinner, next month. "I'm coming back," he beamed.

The 43-year-old Booker, a possible challenger to New Jersey Gov. Chris Christie in 2013, met with both the Iowa and Florida delegations, a sign of his growing national reputation. A regular on cable television and Sunday news shows, the mayor riled some Democrats in May when he criticized Obama's critique of private equity firm Bain Capital, which was co-founded by Romney.

But by Tuesday, all appeared to be forgiven. Booker, a platform co-chair, energized the arena in his address on the opening night, telling delegates, "We are a nation with liberty and justice for all," prompting chants of "USA!"

Earlier in the day, Booker wowed Florida activists despite rolling his ankle on the street outside the downtown hotel housing the delegation. Warning the delegates that "Democracy is not a spectator sport," Booker drew the audience to their feet throughout his breakfast address, prompting some women to wave their white napkins in the air in exultation. "He was so inspirational," gushed state Rep. Lori Berman after his speech.

A presidential bid for Booker may be far off but that doesn't mean people don't ask him about it. Facing TV crews from New York and New Jersey after his Florida address, one reporter asked him: "Can I turn it on you for one moment? 2013? 2016? Gubernatorial run? Presidential run? Don't give me a typical canned answer."

"My life for the next two-plus months is going to be focused on electing Barack Obama," Booker responded. "After that? Fair game. Let's talk anything you want about future elections. But right now, my heart, my soul, my passion, is re-electing the president of the United States."